I have a th400 in my Corvette right now, 406, barely even have to push the gas to get it up to speed, but when Im cruising its all over. Rpms going nuts on the speedometer, makin tons of noise and its not comfortable. Now I dont want to opt for a 2500 Overdrive, or a 1500 t-56 which would probably be the best choice b/c its a good trans and I like the 6 gate shifter and the .5 6th gear overdrive.

Anyway the cheap way out would be a 4+3, which would be nice to have a manual in the corvette, more exicting to drive. Anyway I'd like to know, what kind of gear ratios are the 1-4, and then obviously the overdrive. Also how much power can this trans take, how much does a good scatter shield go for and whats a good clutch, brand, price. Is their any problems mounting it to the 400 block? How hard is it to rebuild the trans and what about the overdrive, unrebuildable? How much does a rebuild kit cost?

I dont need the " Oh dont do it, sell your vette and get a zf-6 version" No I dont need that, I like working on my car and I dont believe that obsurd figure of 4-5K w/o including the actual trans. How hard is it, if your not mechanically minded then your going to have cramps. If its that much a problem, just fab up a new C beam out of steel, add 10lbs of extra weight, fab up a bolt on plate to mount the clutch pedal and mount the slave master, and the driveshaft lengthing or decreasing.

 

Some answers:
http://forums.corvetteforum.com/show...w+much+skspeed

 

Damn, Im already makin 450lbs of tq, add on the turbo now I might break stuff. But other then that, then that would mean I need to find out how to strengthin theoverdrive. So 4th gear is 1;1.

 

TT caloways came with a 4+3, didn't they? Can't be that bad.. Plus you can tell people, that in theory your car has 7 gear ratios

 

I found a site on the gear ratios and I figure its pretty good considering I have soo many problems with the starter, now I can use the push start technique when/if the starter doesnt work on me. Is $350 too much for a 4+3? How much should I pay for the slave master cylinder, line, where could I find a pedal?

Also, how in the heck does the transmission know when to engage the overdrive? ECM driven? If so then Im screwed b/c I use a carb. Is their an external button? Maybe I could get a sphere shifter handle with a button on the side for engaging and disengaging the overdrive?

Plus rebuilding the overdrive, I see that the 4 speed infront is stong, but what about the overdrive unit. And the 84 units where .60 overdrive and the rest where .68 overdrive, Im fine with both but are their any differences between the two?

 

O/d is controlled by the ECM but can be over ridden by the button on the stock shifter ****.ECM was programmed to shift into O/d to save gas.Just hook up a hot feed through a switch to the O/d solenoid and you have manual control;shift in and out of O/d at will.
In later models Z51 option got one ratio and regular cars got the other. No difference that I know off in strength.
Stock "C" beam will fit as differences are related to diff (D36 v D44) not trans, mounts the same auto v manual.
Driveshaft is same length / yoke.
I have just done manual to auto swap and used all the original parts; no changes needed.
Would be to your advanage to get all the stock pieces from a wreck , pedal setup , beam , shaft ,etc to save fabrication time.Have lots of pics of manual setup if your interested.

 

I think your going backwards here by choosing the 4+3… Upgrade to a ZF6 or a Richmond. There is another vender out there offering a 5-speed as well.
Kaiser or something along those lines.

I just did an auto to Richmond 6-sped conversion. Best mod yet

 

In 84 and 85 it wasn't fully ECM controlled.

 

On sad note on the 4+3; the shifter is bolted to the car, not the tranny. It makes for a poor linkage system. I guess it could be mounted to the tranny with some work. The floor is also different because of this (auto vs manual). I happen to have a plaster casting of the 4+3 floor recess if you would like to replicate it in fiberglass.

 

I know its a step back from the 6 speed, but The cheapness of the 4+3 cant be passed up, Plus if I did complete the swap, I'd be able to sell off the th400 which should get me atleast 350 and the convertor mnaybe 75. I just want to get it done and over with and go cruising without 3000rpm in the slow lane.

 

Is the Vette your daily driver?

 

Not at the moment b/c Im using my dads car, but once I get the MSD in the mail and pass smog It will be. Or I can sell it and buy a truck which Im really looking into, had a dodge ramcharger before and was really great. Now Im looking at Dodge ram club cab, 1st generations with a cummins diesel.

It could be that since I drive an F-body ls1 6 speed everyday, I'm starting to feel that the corvette is not really any use to me anymore, If I get a truck I can still drive a sports car which is the F-body. But if I keep the Corvette then I'll have it as my daily driver and the F-body when Im able to drive it. I dunno its a tuff decision and Im leaning more towards buying a truck b/c soo many things wrong with this car, sunvisors, needs new carpet, new tint, door panel is not staying on the door, someone keyed my car and I need to repaint it. But, I want to totally make sure its a good choice so Im not giving up just yet, put too much work into it.

 

In that case I would sell the TH400 and put that money towards a 6-speed. That is if you can wait. I saved for the Richmond and bought what parts I needed over a three year period. I have a friend that was willing to give me a 4+3 for free, but I opted to wait rather than do a job twice.

I think I saw a ZF in the parts for sale section not to long ago for less than 1K, and I think GM is still selling new ones for 1800.00


Edit:As far as practicability you can’t beat a truck. (That’s my daily driver)

Personally I don’t like driving the Vette everyday. I’m always worried about were I park it, it doesn’t turn very sharp and makes getting into and out of parking spaces difficult. Not to mention people drive like A-holes around it, either tailgating you, or wanting to race.

Don’t get me wrong, I love driving it on the weekends, but that’s about it.

 

Im favoring the 4+3 more b/c its cheaper and thats basically it. I just need a better overdrive so I can cruise, I have to drive about 30+ miles a day so if I can get an overdrive in it would save me a ton on gas seeing how expensive it is 2.50/gallon. BTW does your friend still have the 4+3 available? How much do you think I should pay for a used unit?

 

Well if price is the main issue than you’re not going to beat a 4+3. Scorp508 will have a better idea of what the going rate is for a 4+3.

My friend is hanging onto his to use for parts in case anything happens to the unit in the car.

 

I believe they mean 1:1 as in the OD shut off. Wouldn't make much sense if you couldn't accelerate fully until 4th gear...